Biosynthetic achievements including the extension of and permanent attachment to tufts of a person's own hair, i.e. hair that is growing naturally out of the scalp, using genuine and/or artificial hair. Such techniques are used on the one hand for medical applications, though primarily for cosmetic applications. A person's own hair can be lengthened, not to mention thickened, in that a person's own hair and the genuine and/or artificial hair fastened thereto is cut to the same length. In technical fields, a great many systems are known for lengthening and thickening a person's own hair; such systems are described in the 21/94 edition of the "Top Hair Special" magazine. In accordance therewith, a person's own hair can be extended by using artificial or genuine hair by means of special binding and knotting techniques and by various adhesive techniques.
U.S. Pat. No. 5,107,867 describes a hair extension method in which strands of the hair to be extended are joined using a heat-resistant adhesive in order to form a graft on a strand of extension hair, whereupon a coating consisting of a plastic material that is fusible when heat is introduced is applied to this graft. Strands of the person's own natural hair are then threaded through a shrinkable tube portion, the graft of extension hair pretreated in the above-described manner is also inserted into the shrinkable tube and this shrinkable tube treated by application of heat. Either a heating iron, which is described in further detail, or another suitable device can be used. On the one hand, the application of heat causes the tube to shrink, on the other hand the fusible adhesive melts and produces a permanent connection between the natural genuine hair and the strand of extension hair. The tube is intended to protect the connection from environmental influences, but it is also intended to act as a hair care product. If heat is re-applied to the shrinkable tube, the hair extension can be removed once again.
This and other techniques in which adhesives are used make it necessary for a person to after-treat his/her own hair once the hair extension has been removed. Residual adhesive sticking in a person's own hair has to be removed by using a suitable solvent, usually acetone. This results in damage to a person's own hair, particularly as the hair extension methods need to be repeated at regular intervals, approximately every 6 weeks. When solvents are used for such a frequent treatment of the natural hair of the head, a person's own hair may be destroyed at the connecting points.